The present invention relates to a method of cleaning pressurized containers having chemicals contained therein. Specifically, the present invention relates to a method of cleaning pressurized containers such as, for example, rail tank cars, mobile tanks or the like. Further, the chemicals may comprise any material stored under pressure that may be difficult to collect and dispose of due to the hazardous characteristics thereof. Moreover, the chemicals may further be highly reactive to moisture and may form damaging acids or other reaction products when contacting water.
It is, of course, generally known to store and/or transport chemicals having hazardous characteristics via pressurized containers. Further, it is also generally known to clean these containers using a variety of methods and systems. In the past, cleaning pressurized containers entailed venting excess gaseous material to the atmosphere. Further, unpressurized containers contained bottom hatches or valves for draining liquid chemicals. However, many hazardous chemicals escaped into the environment thereby causing health risks for humans, vegetation and wildlife. With the advent of environmental standards and compliance, however, venting or draining hazardous chemicals to the environment has generally become illegal.
Moreover, some chemicals that may be stored within pressurized containers may be highly reactive in the presence of water and may form acids that may be damaging to equipment as well as the environment. Although a flare may be useful to dispose of chemicals that are flammable, some chemicals do not incinerate easily or may form extremely hazardous substances upon incineration. Typically, scrubbers or reaction tanks are necessary to dispose of these chemicals or the byproducts of these chemicals.
While some of the gases contained within the containers may be relatively easy to recover and dispose of by venting the pressurized containers to a flare or to a reaction tank, it is difficult to remove all of the gases contained therein. Further, liquid product may remain inside a container after cleaning. Typical systems and methods of cleaning pressurized containers may involve injecting the container with a quantity of steam that may aid in bringing the liquid chemicals to the gaseous phase and removing the steam/gaseous chemical product combination for incineration or disposal. However, problems may occur using steam to remove chemicals from pressurized containers since steam may condense within the container forming liquid water or ice. The liquid water or ice may mask the presence of the chemicals from detectors or otherwise encapsulate the chemicals. Further, the liquid water or ice may interfere with the removal of the chemicals from the container. Moreover, liquid water or steam may react with certain chemicals, such as for example, chlorine gas or sulfur dioxide gas, to form hazardous byproducts, such as acids, that may damage equipment or the environment if released. For example, chlorine gas and sulfur dioxide gas may react with water according to the following reactions to form hydrochloric acid and hydrochlorous acid, and sulfuric acid, respectively:
Cl2+H2Oxe2x86x92HCl+HOClxe2x80x83xe2x80x831.
2SO2+2H2O+O2xe2x86x922H2SO4xe2x80x83xe2x80x832.
In addition, steam or liquid water may be difficult to remove from the container since water droplets may stick to the inside surfaces of the container, piping and/or equipment. A further step would be required for drying the container and/or the equipment, thereby requiring additional time, equipment and expense.
Another method of removal may include entering the container to manually remove the chemical and/or any other debris, such as, for example, scaling, that may be contained within the container. While this may be a relatively thorough way to remove the chemical from the container, it may be very dangerous, as it requires an individual to actually enter the container thereby exposing the individual to any chemicals that may be contained therein. Further, by opening the container, there may be a significant risk that some of the chemicals may escape into the environment.
Therefore, an improved method of cleaning pressurized containers is necessary. Particularly, a method is needed that overcomes the problems associated with typical cleaning methods. Further, a method is needed that cleanly and efficiently removes chemicals from a pressurized container and transports the waste product to a proper disposal apparatus, such as a flare or a reaction tank, to incinerate or otherwise safely dispose of the chemicals.
The present invention relates to a method of cleaning a pressurized container having chemicals therein. More specifically, the present invention allows mobile containers such as, for example, rail tank cars, to be cleaned safely and efficiently without risking exposure of the chemicals to people or the environment. The invention entails injecting heated and pressurized nitrogen gas or heated and dry air into the container thereby purging the container of any chemical therein and forming a nitrogen/chemical mixture. The nitrogen/chemical mixture may then be sent to a flare for incineration or a reaction tank for neutralization of the chemical. Further, the heated nitrogen gas may aid in pulling the chemical out of the container and transporting the chemical to the flare for incineration. In addition, a vacuum pump may be utilized to further aid in the removal of the nitrogen/chemical mixture from the container.
To this end, in an embodiment of the present invention, a method of cleaning pressurized containers containing chemicals is provided. The method comprises the steps of: providing a pressurized container having a quantity of a chemical contained therein; providing an input gas; injecting the input gas into the pressurized container via a first valve to form a chemical/input gas mixture within the pressurized container; removing the chemical/input gas mixture from the pressurized container via a vacuum pump; and disposing of the chemical/input gas mixture.
The method further comprises the step of removing the chemical from the container via the vacuum pump prior to injecting the heated input gas into the container. Moreover, the pressurized container is a rail tank car. Further, the container is disposed on a vehicle.
The method further comprises the step of heating the input gas prior to injecting the input gas into the pressurized container. Moreover, the method further comprises the step of heating the input gas to a temperature of between about 100xc2x0 F. and about 300xc2x0 F. prior to injecting the input gas into the pressurized container.
In a further embodiment of the present invention, the method comprises the steps: of providing an input pipe attached to the pressurized container via a first valve; providing an output pipe attached to the pressurized container via a second valve on a first end of the output pipe and a disposal means on a second end of the output pipe; and closing the second valve and opening the first valve when injecting the input gas into the container.
Still further, the method comprises the step of closing the first valve and opening the second valve when removing the chemical or chemical/input gas mixture via the vacuum pump. Moreover, the method comprises the step of providing a control means for controlling the injection of the input gas and removal of the chemical/input gas mixture.
In a further embodiment of the present invention, the method comprises the steps of: providing a control means for automatically controlling the injection of the input gas and removal of the chemical/input gas mixture; and controlling the injection of the heated input gas to the container via the controller. The method further comprises the steps of: providing a plurality of valves on the container; and opening up a first valve to inject the container with the heated input gas to form a chemical/input gas mixture.
The method further comprises the steps of: closing the first valve when the container is sufficiently pressurized; and opening a second valve to remove the chemical/input gas mixture. Moreover, the method comprises the step of synchronizing the opening and closing of the first and second valves so that the first valve is closed when the second valve is open and the first valve is open when the second valve is closed.
In a still further embodiment of the present invention, the method comprises the step of synchronizing the injection of the heated gas and the removal of the chemical/input gas mixture. Moreover, the synchronization step is performed via a control means.
Moreover, the method further comprises the steps of providing a reaction tank containing a neutralizing material; and injecting the chemical/input gas mixture into a reaction tank to neutralize the chemical. Further, the neutralizing material comprises a caustic solution. Still further, the neutralizing material is selected from the group consisting of sodium hydroxide, potassium hydroxide, sodium carbonate, calcium hydroxide, sodium sulfite, sodium thiosulfite, ferrous chloride and solid bed absorbents. In addition, the chemical/input gas mixture flows through the reaction tank and the chemical reacts with the neutralizing material to form a salt.
It is, therefore, an advantage of the present invention to provide a method of cleaning a pressurized container having a quantity of chemicals therein that safely and efficiently removes chemicals from the container. Moreover, it is advantageous that the present invention removes chemicals from the container without risking exposure to people or the environment.
Further, it is an advantage of the present invention to provide a method of cleaning a pressurized container having a quantity of chemicals therein that allows the chemicals to be removed without causing damage to the container by freezing the container or pipes connected thereto. In addition, an advantage of the present invention is that the heated nitrogen gas used to remove the chemical will not condense within the container and therefore will not mask the presence of the chemicals therein.
Another advantage of the present invention is to provide a method of cleaning a pressurized container having a quantity of chemicals therein that is largely automatic and therefore allows an individual to monitor the process without exposing the individual to the chemicals. Additionally, an advantage of the present invention is that a plurality of types of containers may be cleaned using the method defined herein, including, but not limited to, rail tank cars and other like containers.
A still further advantage of the present invention is to provide a method of cleaning a pressurized container having a quantity of chemicals therein that utilizes a vacuum pump to remove chemicals from the container and to create a vacuum in the container to aid in the injection of heated nitrogen gas to the container.
Additional features and advantages of the present invention are described in and will be apparent from, the detailed description of the presently preferred embodiments and from the drawings.